// 构造函数，类的一部分，
var Book = function(isbn,title,author){ //函数表达
    this.isbn = isbn;
    this.title = title;
    this.author = author;
}
Book.prototype = {
    checkIsbn : function(){},
    borrow: function(){console.log('Book的');}
    
}
var xhs = new Book('978-7-115-19128-1/TP','你不知道的JavaScript','KYLE');
xhs.borrow();
// 空对象
var sjms = {borrow: function(){console.log('自己的');}};
Book.call(sjms,'857-4444','葵花宝典','金庸')
sjms.__proto__=Book.prototype
sjms.borrow();
console.log(sjms.__proto__);
console.log(Book.prototype.__proto__);
sjms.borrow();
console.log(sjms.toString());